The influence of Cu, Ag, and Au additives on the L1 0 ordering, texture, and grain size of FePt thin films has been examined. Lattice parameter data indicated that Au and Ag additives tended to segregate from FePt, but Cu alloyed with FePt. FePt films with Au or Ag additive showed 1-2 kOe higher coercivity values compared to a pure FePt film after annealing at 450°C and above for 10 min. The addition of at least 20 vol. % Cu to FePt boosted average coercivity values and increased ͑001͒/͑002͒ x-ray peak intensity ratios, suggesting an accelerated L1 0 ordering process for annealing temperatures exceeding 350°C. Decreasing the film thickness promoted ͑001͒ film texture in FePtϩ20% Cu films, but higher annealing temperatures were required to achieve large coercivity. Au and Ag limited the average grain size compared to a pure FePt film. Cu additive increased the average grain size and film roughness.
A noneptaxially grown double-layered thin-film medium of nanocompsite FePt:C with a FeCoNi soft underlayer for high-density perpendicular magnetic recording was fabricated and investigated. Square-shaped perpendicular loops with a remanance ratio nearly equal to one and a coercivity as large as 8.5 kOe were obtained for this ordered FePt:C double-layered medium. The formation of the ordered L10 phase is confirmed by electron diffraction experiments. Transmission electron microscope observations reveal that FePt grains with a uniform size less than 5 nm are embedded in the C matrix and appear to be well isolated. Our results show that nonepitaxially grown (001) textured double-layered nanocomposite L10 FePt-based films with perpendicular anisotropy are a promising candidate to realize extremely high-density perpendicular recording.
Optically thick films of MnPt 3 were deposited on quartz using dc magnetron sputtering. The films were covered with an SiO x protective overcoat and annealed in vacuum at 850°C for 1 h to form the crystalline L1 2 ͑Cu 3 Au͒ cubic structure. These films have a high degree of long-range order and are highly textured with the ͑111͒ axis along the film normal. Variable angle spectroscopic ellipsometry measurements were taken over the spectral range of 1.2-4.2 eV to determine the optical constants of both MnPt 3 and the SiO x overcoat. Spectroscopic magneto-optic Kerr rotation and ellipticity measurements at near normal incidence over the spectral range of 1.4-3.6 eV were used to determine the off-diagonal dielectric tensor elements for MnPt 3 . Firstprinciples electronic-structure calculations were carried out for the ordered MnPt 3 structure and from these the dielectric tensor elements of MnPt 3 were calculated. The experimental and theoretical values of the diagonal components of the dielectric tensor components are in good agreement. The agreement for the off-diagonal components of the dielectric tensor is only fair. ͓S0163-1829͑97͒04205-7͔
Differential scanning calorimetry, in conjunction with x-ray and electron diffraction, is used to investigate the A1 to L10 ordering transformation in binary FePt films with compositions in the range of 47.5–54.4at.% Fe. The kinetic ordering temperature, taken as the calorimetric peak temperature at a heating rate of 40°C∕min, decreases from 447to357°C in this composition range. In contrast with the kinetic ordering temperature, the Curie temperature of the L10 ordered phase increases from 384to455°C as the Fe content is increased. The activation energies of ordering lie between 1.4 and 2.0eV, and the transformation enthalpies are in the range of −8.2to−13.6kJ∕g-at. The Avrami exponent for the transformation is lower than expected and lies in the range of 1.1–1.8. The lattice parameter of the A1 phase and the c∕a ratio of the L10 phase decrease with increasing Fe content.
The evolution of stress in 50 nm FexPt1−x (x=0.41, 0.43, 0.49, 0.52, and 0.56) sputtered films was monitored in situ as a function of the temperature. In the as-deposited state, films have a disordered face-centered-cubic (fcc) structure with a strong (111) fiber texture and 685–978 MPa compressive stress. Below 200 °C, thermal expansion of the FexPt1−x fcc lattice produced an initial increase in residual in-plane compressive stress. Above 250 °C, a transition to a low stress state was observed, with the relaxation in the Fe0.52Pt0.48 film showing stronger temperature dependence. Comparisons of stress to a sputtered film of Fe0.35Cu0.15Pt0.5 indicate a faster transition rate to the low stress state can be achieved with the addition of Cu. In situ high temperature x-ray diffraction measurements show a decrease in (111) d spacing with an increase in temperature, and are consistent with the changes observed in the residual stress measurements. The large stress transition appears to arise from changes in the fcc phase prior to L10 phase transformation, because a substantial increase in film coercivity appears only after the transition to the low stress state has been completed.
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